The disclosed invention generally relates to digital-to-analog converters and analog-to-digital converters, and is particularly directed to a switched capacitor array for use in multi-stage converters and which provides reduced differential non-linearities resulting from coupling one stage to another.
Digital-to-analog (D/A) converters are utilized to provide an analog signal, such as a voltage, as a function of a digital input. Analog-to-digital (A/D) converters are utilized in systems wherein analog signals, such as those provided by analog transducers, are processed digitally.
Conversion of digital signals having a large number of bits (e.g., eights bits or greater) may be more advantageously provided with the use of staged digital-to-analog converters wherein the digital signals are divided into groups which are then converted by respective staged digital-to-analog converters. The staged digital-to-analog converters are cascaded so that the output of the converter for the least significant group of bits is coupled as an input to the converter for next significant group, and so forth. For converters that utilize capacitors as the weighting elements, such coupling is provided an LSB capacitor, which scales the contribution of the group of bits having lesser significance or weight.
However, the use of an LSB capacitor results in differential nonlinearity where the LSB capacitor is not precisely the same value as the other capacitors of the stage receiving the input from a converter stage of lesser significance.